If you’re a gardener in Southern California, figuring out when to plant sweet potatoes is your first step to a great harvest. The optimal timing for planting here is a bit different than in other parts of the country, thanks to our wonderfully long, warm growing season.
You have a big advantage with our climate. Sweet potatoes love heat and sun, and we have plenty of both. Getting the timing right means your plants will grow strong and produce those tasty tubers you’re looking forward to.
When to Plant Sweet Potatoes in Southern California – Optimal Timing for Planting
The golden rule for Southern California is to plant sweet potato slips after the last spring frost and when the soil is truly warm. While we have mild winters, a cold snap can still shock these tropical plants.
For most areas, the ideal planting window is from late April through June. Coastal zones can start in late April or May. Inland valleys and warmer desert areas can plant from May into early June. The goal is to have soil temperatures consistently above 65°F, but 70°F is even better.
Planting too early in cold soil will stunt growth. Planting by mid-June ensures your crop matures in the peak summer heat before fall cools down.
Why Timing is Everything for Sweet Potatoes
Sweet potatoes aren’t related to regular potatoes. They are a member of the morning glory family and need sustained warmth. Their growth cycle depends on it.
Here’s what happens with correct timing:
- Root Development: Warm soil encourages slips to quickly establish roots.
- Vine Growth: Ample sun and heat fuel the vigorous leafy vines.
- Tuber Formation: Tubers begin forming in response to the shortening day length in late summer, but they need warm soil to bulk up.
If you plant to late, the tubers won’t have enough time to size up before cooler soil halts their growth. It’s a balancing act you can master.
Preparing Your Garden Bed
Sweet potatoes aren’t super picky about soil fertility, but they demand excellent drainage. They prefer a slightly acidic to neutral pH.
Follow these steps to prepare:
- Choose a Sunny Spot: Full sun is non-negotiable—at least 6-8 hours of direct sun daily.
- Loosen the Soil: Dig or till the bed to a depth of 10-12 inches. These tubers need loose soil to expand.
- Amend for Drainage: If you have heavy clay, mix in generous amounts of compost or well-rotted manure. Raised beds are an excellent option.
- Skip the Nitrogen: Avoid high-nitrogen fertilizers. They promote leafy vines at the expense of tuber growth. A light dusting of a balanced organic fertilizer or some bone meal is plenty.
Selecting the Right Varieties
Choosing a variety suited to our season length is smart. Some good choices for SoCal include:
- Beauregard: A reliable, fast-maturing classic with copper skin and orange flesh.
- Georgia Jet: Another fast grower, good for areas with slightly shorter warm seasons.
- O’Henry: A white-fleshed variety with a creamy texture and good yield.
- Japanese Purple: Striking purple skin and flesh, holds its color well when cooked.
How to Plant Your Sweet Potato Slips
You won’t plant seeds, but “slips,” which are small rooted sprouts. You can buy them or grow your own from a sweet potato.
- Harden Off Slips: If your slips were mail-ordered or grown indoors, acclimate them to outdoor sun for a few days.
- Planting Depth & Spacing: Plant slips deep, burying the stem up to the first set of leaves. This encourages more root formation along the stem. Space slips about 12-18 inches apart in rows 3 feet apart.
- Water Thoroughly: Water them in well to settle the soil and reduce transplant shock.
- Consider Black Plastic: Using black plastic mulch is a fantastic trick. It warms the soil further, suppresses weeds, and conserves water. Just cut holes for your slips.
Caring for Your Growing Sweet Potatoes
Once established, sweet potatoes are quite drought-tolerant and low-maintenance.
- Watering: Water deeply once a week to encourage deep roots. Taper off watering in the last 3-4 weeks before harvest to help the tubers cure and develop their sweetness.
- Weeding: Weed carefully early on. Once the vines spread, they’ll shade out most weeds on there own.
- Feeding: Usually not needed if your soil was prepared well. A side dressing of compost mid-season is sufficient if growth seems slow.
- Pest Watch: Keep an eye out for gophers and ground squirrels, who love the tubers. Deer may browse the vines. Row covers can protect young plants from pests.
The All-Important Harvest and Curing
Knowing when to harvest is as crucial as knowing when to plant. Your tubers are ready about 90-120 days after planting.
Signs of readiness include yellowing leaves and the approach of your first expected fall frost (though ours is late). The best test is to gently dig around a plant to check tuber size.
- Harvest on a Dry Day: Use a digging fork carefully to avoid bruising the delicate skins.
- Curing is Essential: This step converts starches to sugars and heals minor wounds. Never skip it! Place undamaged tubers in a warm (80-85°F), humid place for 10-14 days. A shaded outdoor area or a garage often works.
- Storage: After curing, store your sweet potatoes in a cool (55-60°F), dark, and well-ventilated place. Properly cured, they can last for months.
Common Mistakes to Avoid
- Planting in cold, wet spring soil.
- Using soil that is to rich in nitrogen.
- Overwatering, especially close to harvest time.
- Harvesting to late after vines have been hit by cold.
- Not curing the tubers before storage, leading to poor flavor and rot.
FAQ: Sweet Potatoes in Southern California
Can I plant sweet potatoes in July?
It’s generally to late for a main crop, but you could try for a smaller harvest of “baby” sweet potatoes. Opt for a fast-maturing variety like Georgia Jet.
What’s the difference between a slip and a seed?
Sweet potatoes are grown from vegetative sprouts called slips, not true seeds. This ensures the new plant is a clone of the parent with consistent traits.
How long do sweet potatoes take to grow?
Most varieties need 90 to 120 frost-free days from planting to reach full maturity. Our long season is perfect for this.
Can I grow sweet potatoes in containers?
Absolutely. Use a large container (at least 20 gallons) with excellent drainage. A fabric grow bag is a great choice, as it prevents circling roots and allows easy harvest.
Why are my plants all vines and no potatoes?
This is often caused by to much nitrogen in the soil, overcrowding, or insufficient sunlight. Ensure you prepared your bed correctly and chose a sunny location.
With the right timing and simple care, growing sweet potatoes in Southern California is a rewarding endevor. Your patience will be rewarded with a homegrown harvest that’s sweeter than anything you can buy.